Heat exchanger



`April 28,1925.

J. 'A. STAlRs mm: Excrmcmn Filed Feb. '7. 1924.

4v Sheets-'Sheet 2 INVENTOR April 2s, 1925 J. A. STAIRS HEAT EXCHANGER Filed Feb. '7. 1924 4`Sheets-Sheet 5 4 1. i ,fl v .K l AO. l I I .D

Patented Apr. 28, i925.

U EID- STA T ES- TAMES A. S'la'iIIR-S, OF PITTSBURGH,

1,535,35l P T EN Trv OF l C E.V

PENNSYLVANIA, ASSIGNOR T0 THE CALORIZING COMPANY, OF PITTSBURGH, PENNSYLVANIA,

A CORPORATION OF DELAWARE.

HEAT EXCI-IANGER.

Application filed February 7, 1924.

To all 'whom t may concern.'

Be it known that I, JAMns A. STA-Ins, a subject ofj the King of England, residingv at Pittsburgh, county of Allegheny, State of Pennsylvania, United States of America, have invented new and useful Improvements iny Heat Exchangers,` of whiclr the following .is a full, clear, and exact description.`

Ther present inventionrelates broadly to heat exchangers, heat exchangers of the character usually referred as recuperato-rs.

While it liasheretofore been proposed to utilize different connection withvarious forms of furnaces7 there have been some objections thereto, particularly in larger furnace installations.

Ordinarilyrecuperators have been designed inrcach instance for the furnacewith which they were to` be used. This has necessarily resulted ina special` construction requin skilled labor for each installation. Also,

with the very large furnaces the length of the reouperator has` frequently been such:

that there has been an objectionable pres@ sure drop therethrough.

In accordance with the present invention, the recuperator preferably comprises a series of `standard units adapted to be easily connected at will by unskilled labor to form a complete heat exchangerof any desired length and adapted to a wide variety ofI furnaces.` Each, unit has a comparatively short flow path therethrough,.providing for efiicient heat transfer 'without' any objectionablcl pressure drop.

Another object ofkthe present invention is to provide an apparatus of the character referred to havino a maximum heat transfer surface, together with a comparatively high velocity ofthe Huid which is absorbing` heat.

In the accompanying drawings I have shown, for purposes of illustration. only, a preferredembodiment of the presentinvention, it being understood' that'. the drawings do not limit the invention, as changes in the construction and operation therein disclosed may benna-de without departing from the spirit of the. invention or. scope of my broader claims.

In the drawings-` Figure l is a top plan. view illustrating a heat exchanger constructed inv accordance and more particularly to.

forms of recuperators in` ferred in a heat exchanger- SeriallNo. 691,148'.

with the present Figure 2 is a vertical transverse sectional view on the line II-II of Figurel looking in the direction of the arrows;

Figure 3 is a vertical*longitudinalV sectional view on the lin-e III-III of Figure l lookingiir the direction of the arrows;

V.Figure t isa perspective view ofone form of. unit utilized in constructing a complete heat exchanger; and

`Figure 5 isa view similar to Figure l illustrating a slightly; modified form of unit.

Itfis well recognized that the heattranscharacter. contemplated by the present applicationfisdependent to a large extent uponv the velocity of flow of the absorbing heat. locity as high as provide comparatively short paths of How to thereby minimize the pressure drop. At the Sametime, it'i's desirable'to so construct the heat` exchanger that a comparatively large heat transfer surface, enabling etlicient heat transfer, is; provided.

Furthermore in the interest of ease of installation and'` flexibility of construction, it is desirable to provide a heat exchanger which may; bemade up at will of standard sections or units adapted to be connectedin operative relation to various forms of furnaces by unskilledY labor.

The' foregoing advantageous features of' construction are embodied in a heat eX- changer of the character shown her-ein as disclosed in cooperative relation to a car type annealing furnace; In' the drawing, there is illustrated. a furnace 2 which may obviously bey ofv any. desired, construction but which is here shown as comprising an annealing furnace of thecar type. Such a furnace is ordinarily provided with a pluralityof' burner openings 3 by means of which' the desired temperature conditions may be maintained therein. Extending vertically through. thewalls of the furnace is a plurality` of ductst adapted to convey waste gases from the annealing chamber 5. These waste gases ordinarily leave the. furnace at a comparatively high temperature, thereby making it desirable to provide some means of recovering,.to as large an extent as possible, the waste heat therefrom..

Iny accordance with my invention this fluid which is In order to keep this ve` invention in cooperative relation with a furnace;

ofr the general' possible, it is essential to heat recovering means is disclosed as comprising a recuperator composed of a plurality of sections or units 6, 7 and 8 extending in end to end relationship throughout any desired length of the furnace. Each of the sections or units G, as disclosed in detail in Figure 4, preferably comprises an inner casing 9 and an outer casing 10. The inner casing is preferably formed into substantially inverted U shape having an open bottom 11 adapted to straddle the ducts 4 and permit the waste gases to freely enter the same. The peripheral edges of the inner casing are bent outwardly to form end flanges 12 for cooperation with adjacent units and bottom flanges 13, insuring the necessary stability of installation. The outer casing of each of the units is similarly shaped but is of such dimensions as to provide a chamber 14 between the casings. The outer casing may also be formed with flanged edges adapted to cooperate with the flanges before referred to, to enable the casings to be welded or otherwise secured in position.

Cooperating with one corner of each of the units 6 to permit the passage into the chamber 14 of the inlet 15, while cooperating with a diagonally opposite corner is an outlet 15. While this construction is such that fluid passing from the inlet to the outlet would necessarily absorb a considerable portion of heat from waste gases within the inner casing, I have found that the efficiency may be considerably increased by the provision of interior baflles 17 adapted to cause the fluid to be heated to flow through the chamber 14 in a tortuous path. These baffles may conveniently comprise angles suitably secured to the inner casing with alternate baffles having different ends cut away to permit the fluid to flow through the chamber 14, as indicated by the arrows A. rEhe path of travel formed in this manner is not long enough to cause any objectionable pressure drop in the fluid flowing through any one unit and, by reason of the relatively smaller cross sectional area provided at any one point for the flow of fluid, insures its passage through the units at a relatively higher velocity.

Each of the units 7 is preferably of a construction similar to that shown in Figure 4, with the exception that there is provided in such units a vent 18, permitting the escape of the waste gases to the atmosphere or to a stack. Where such vent is provided, the baffles 17 as shown in Figure 5 are preferably so positioned as to compensate for the decreased area caused by the vent and provide for a more nearly uniform flow of the fluid through the units, as will be clearly understood. While the units 6 and 7 may be arranged in any defluid to be heated is an sired order, I have found that advantageous results are produced where they are alternated, as clearly indicated in Figure l.

At suitable points throughout the length of a heat exchanger there may be provided units 8 embodying all of the features of construction shown in Figure 5. Ordinarily, however, a single one of these units in each assembly will be sufficient. These units 8 differ from the units 7 in the provision of spacing sleeves 19 suitably secured to the inner casing 9 and projecting outwardly therefrom. Each of these sleeves has a length substantially equal to the distance between the inner and outer casings and has an integral diamter sufficient to permit the passage therethrough of bolts 20 serving to support longitudinally extending pipes 21 within the waste gas chamber for the purpose hereinafter more fully pointed out. It will be understood that the bolts 2O may be held in position by suitable nuts (not shown) threaded upon the outer ends and that the spacing sleeves serve to prevent relative collapse of the inner and outer casings when the nuts are screwed into position.

For supplying air simultaneously to all of the units and for connecting the same in parallel in such manner that there is au individual flow therethrough, there may be provided a distributing pipe 22 having branch outlets 23 communicating with each of the inlets 15 of the respective units. Connected to each of the outlets 16 is a collecting pipe 24 having a suitable closure 25 for one end and communicating at its opposite end with the interior of a header 26. This header may be formed with flanges 27 adapted to cooperate with the end flanges of the unit against which it abuts and provide for the clamping therebetween of a plate 28 serving as a holding means for the pipes 21. In this manner the fluid previously heated by its passage between the inner and outer casings of the different units is further caused to pass longitudinally through all of the units by means of the pipes 21. At their opposite ends these pipes are mounted in a similar plate 29 and deliver to a header 30 in coinmunication with a hot air pipe 31 adapted to deliver the heated air or other fluid to the burners.

Each of the units, as well as the pipes, bolts and spacer sleeves used in the construction of a complete heat exchanger may conveniently be formed of calorized metal, whereby oxidation thereof at the high temperatures to which they are subjected is prevented. Where the parts are individually caloriZed before assembly, the abutting surfaces inay be ground or otherwise cleaned to permit the welding or other oining together thereof, as may be desired.

The arrangement of units described may duplicated on opposite sides of a furnace asl indicated in Figures l and 2, where such duplication is of advantage, and the number of units assembled in end to end relationshlp may be increased or decreased to provide a. complete heat exchanger having l't will also any required over-all lengt-h.

be apparent that the construction ofthe units issuch that they may be reversed end to end by utilizing the inlets 1,5 asV- the outlets in this manner the assembly of the complete heat exchanger may properly be effected by unskilled labor, the individual units conveniently being' secured in cooperative relation by suitable fastening means extending through aligning openings 32 in the end flanges thereof.

In order to reduce heat loss by radiation to a minimum, each of the units may be covered with a suitable insulating material 33, as indicated in Figures 4 and 5.

The advantages of the present invention arise from the provision of a heat exchanger comprising a plurality of units adapted to be assembled at will in such manner `as to provide an initial parallel flow therethrough of the fluid to be heated.

Still further advantages of the invention arise from the provision of units adapted to be assembled by unskilled labor and reversible at will to provide greater flexibility in the assembling and handling thereof.

Further advantages of the invention arise from the construction of each of the units whereby a maximum heat transfer therein is insurec.

I claim:

l. The combination with a furnace, of a plurality of recuperator units arranged in end to end relationship lengthwise of the furnace and adapted to receive waste gases from the furnace, and means connecting said units in parallel for producing' an initial fluid flow individually therethrough, substantially as described.

2. The combination with a furnace, of a plurality of recuperator units arranged in end to end relationship and adapted to receive waste gases from the furnace, means connecting said units in parallel for producing an initial fluid flow individually therethrough, and means for thereafter passing all of the fluid through said units in series, substantially as described.

3- The combination with a furnace, of a plurality of recuperator units arranged in end to end relationship, each of said units having' an inner chamber adapted to receive waste gases from the furnace and an outer chamber to receive the fluid tobe heated, means connecting said units in parallel for producing an initial fluid flow simultaneously through all of said outer chambers, and means for thereafter passing' all of the fluid serially through. said inner chambers, subf stantially as described.`

4.. The combination with a furnace, of a plurality of individually removable recuper-` ator units arranged in end to end relationship, each` of said units having; an inner chamber adapted tozreceive waste gases from the furnace and an outer chamber to receive they fluid toV beheated, and means-'connecting said units in parallel for producing an initialr fluid flow simultaneously through all of said outer chambers,` substantially as described.

5.- A heat exchanger, ity of. individually removable units adapted to be connected in end to end relationship lengthwise of a furnace, and having separate passages therein for the different fluids, substantially as described.

6. A heat exchanger, comprising a plurality of inverted U-shaped flanged units adapted to be connected in end to end relationship, and having separate passages therein for the different fluids, substantially as described.

7. A heat exchanger, comprising a plurality of units connected in end toend relationship and adapted to receive waste gases from a furnace, at least one pipe extending through all of said units, means for initially passing a fluid through said units in parallel, and means for thereafter conducting such fluid to said pipe, substantially as described.

8. A heat exchanger, comprising a plurality of units assembled in end to end relationship and adapted to receive waste gases from a furnace, at least one pipe extending through all. of said units, means for initially passing a fluid through said units in parallel, and headers cooperating with the end units and with said pipe for thereafter conducting such fluid to said pipe, substantially as described.

9. A heat exchanger unit, comprising an inner casing adapted to receive waste gases, an outer casing spaced from the inner casing and providinga chamber between said casings, and an inlet and outlet for said chamber, substantially as described.

l0. A heat exchanger unit, comprising an inner casing adapted to receive waste gases, an outer casing spaced from the inner casing and providing a chamber between said casings, an inlet and outlet for said chamber, and means insuring a tortuous flow between said inlet and outlet, substantially as described.

ll. A heat exchanger unit, comprising an inner casing having flanged peripheral edges, an outer casing spaced from the inner casing and providing a chamber between said casings, said outer casing having flanges to cooperate with the flanges on the inner casino' and means for conducting a comprising a. pluralluid to and from the chamber between said casings, substantially as described.

12. A heat exchanger unit, comprisingan inner casing` of substantially inverted shape adapted to receive waste gases through its open bottoin end, an outer casing spaced troni the inner casing and providing a chamber between said casings, and means for conducting a fluid to and from said chamber, substantially as described.

13. A heat exchanger unit, comprising' an inner casing of substantially inverted U shape adapted to receive waste gases through its open bottoni end, an outer casing spaced troni the inner casing and providing a chainber between said casings, lneans for conducting' a fluid to and from said chamber, and inea-ns carried by said unit for supporting' a pipe within said inner casing, substantially as described.

14. A heat exchanger unit, comprising,` an inner casing adapted to receive waste gases, an outer casing' spaced from the inner casing and providing a chamber between said casings, an inlet and outlet for said charnber, and heat insulating means for said unit` substantially as described.

1n testimony whereof I have hereunto set iny hand.

JAMES A'. STAIRS. 

